Biologists Uncover How Plants Sense Heat during Day

New research by the University of California, the riverside professor, Meng Chen, shows that plants are based on several heat detection systems and that sugar – produces in the sun – plays a central role and previously unrecognized in the response of daytime temperature.

Arabidopsis The plants grow in a greenhouse. Image credit: Elena Zhukova / UCR.

“Our textbooks say that proteins like phytochrome B and early flowers 3 (Elf3) are the main thermocapper of plants,” said Professor Chen.

“But these models are based on night data.”

“We wanted to know what is happening during the day, when the light and the temperature are both raised because these are the conditions that most plants really experience.”

To investigate, Professor Chen and his colleagues used ArabidopsisA small, privileged flower plant in genetics laboratories.

They exposed sowing to a range of temperatures, from 12 to 27 degrees Celsius, under different light conditions, and followed the extension of their sowing stems, called hypocotyles – a classic indicator of heat growth response.

They found that phytochrome B, a light detection protein, could only detect heat under low light. In light conditions that imitate the midday sun, its temperature detection function has actually been stopped.

However, plants have also responded to heat, increasingly when the role of thermocadaver in phytochrome B has been considerably reduced.

“This underlined the presence of other sensors,” said Professor Chen.

An index came from the studies of a phytochrome mutant B devoid of its thermocadarator function.

These mutant plants could only respond to heat when they are cultivated in the light.

When they are cultivated in darkness, without photosynthesis, they lacked chloroplasts and were not higher in response to heat.

But when the researchers completed the growing environment with sugar, the temperature response returned.

“It was then that we realized that sugar did not only make growth. It was acting like a signal, saying to the plant it is hot,” said Professor Chen.

Other experiments have shown that higher temperatures have triggered the degradation of starch stored in the leaves, releasing sucrose.

This sugar in turn stabilized a protein known as PIF4, a master regulator of growth. Without sucrose, Pif4 deteriorated quickly. With him, the protein has accumulated but only became active when another sensor, Elf3, also responded to the heat while deviating.

“Pif4 needs two things. Sugar to stay and free themselves from repression. Temperature helps provide both,” said Professor Chen.

The study reveals a nuanced multilayer system. During the day, when light is used as a source of energy to fix carbon dioxide in sugar, plants have also changed a sugar -based mechanism to detect environmental changes.

As temperatures increase, stored starch turns into sugar, which then allows key growth proteins to do their work.

The results could have practical implications. As climate change leads to extreme temperatures, understand how and when plants smell heat could help scientists raise crops that are growing more and more predictable and more resilient under stress.

“This changes the way we think of the thermalians in plants,” said Professor Chen.

“It is not only a question of proteins that turn around or undress. It is also energy, light, sugar.”

“The results also underline, once again, the quiet sophistication of the plant world.”

“In the blurring of photosynthesis and starch reserves, there is a hidden intelligence.”

“The one who knows, gently and precisely, when it is time to extend to the sky.”

The study was published in the journal Nature communications.

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D. Fan and al. 2025. A multisensor high temperature signaling frame to trigger a diurnal thermomorphogenesis in Arabidopsis. Nat common 16, 5197; DOI: 10.1038 / S41467-025-60498-7